The present invention relates to a link mechanism utilized for a panhard rod (a lateral rod) and so forth in five-link-type rear suspension for an automobile.
Conventionally, this kind of link for example, as a panhard rod, which is used for a rear suspension is shown in FIG. 1 (referring to "New Version Structure of chassis 1!" published by K. K. Sankaido, Mar. 25, 1995, pages 200 to 201). The rear suspension is a five-link-type suspension, in which an axle case 1 is suspended from a car body, the rear suspension includes lower links 3 at right and left thereof, upper links 5 at right and left thereof (only illustrated right side portion of the body width lateral direction), shock absorbers 7 at right and left thereof, and coil sprigs 9 at right and left thereof, and further includes a panhard rod 11 as a link. The right end of the body width lateral direction of the panhard rod 11 is supported on the case side bracket (not illustrated), which is mounted on the axle case 1, while the left end thereof is supported being body side bracket (not illustrated), which is mounted on the portion of the car body side. Further, the case side bracket which transmits the vibration from the differential device to the panhard rod 11 through the axle case 1, becomes an exciting side portion, while the body side bracket becomes a receiving side portion.
Such panhard rod 11 is constituted as shown in FIG. 2. Namely, the panhard rod 11 has collar sections 17a, 17b on both ends of a hollow rod section 15. A mass 19 for limiting vibration is fixed to the collar section 17b. One collar section 17a is supported on the body side bracket being receiving side portion through a bushing of an elastic body not illustrated. The other collar section 17b is supported being case side bracket 13 on the exciting side portion through a bushing of an elastic body not illustrated. Consequently, the lateral force input from the wheel toward the axle shaft 1 is capable of being supported by the panhard rod 11 to the car body side.
Now, if the panhard rod 11 is supported as described above, the vibration (different whine) at for example approximately 400 Hz caused by engagement of differential device supported on the inside of the axle case 1 is imputed to the panhard rod 11 through the axle case 1 and the case side bracket. Furthermore, this vibration is imputed to the car body through the body side bracket, so there is fear that the vibration causes the room noise of the car body. This is attributed to the fact that the panhard rod 11 bending-vibrates with the mode such as representation of the chain line of FIG. 3 by the diff noise. Further, although only FIG. 3 shows the primary vibration and the secondary vibration, other multiple vibration exist. Namely, the nodes 21 of the bending vibration mode exist on the rod section 15 of the panhard rod 11, while the nodes 21 do not exist on the principal inertia axis of the bushings on the inside of the collar sections 17a, 17b, the collar sections 17a, 17b vibrate in the direction of up and down such as the arrows N, so that the diff noise is transmitted to the car body.
For this reason, conventionally, the mass 19 is provided thereto, and the vibration of the collar section 17b is suppressed by weight of the mass 19, with the result that transmission of the vibration to the car body is regulated. Further, in order to suppress the vibration of the collar sections 17a, 17b by the mass 19, it causes the weight thereof to increase as large as possible.
However, the mass 19 is regulated in the supported condition in such a way that the mass 19 does not enter into the portion 23 indicated by hatching of FIG. 2, in relation to the case side bracket 13 which supports the collar section 17b or another parts. Consequently, the mass 19 is incapable of being enlarged unlimitedly so that there are limits of vibration-suppressing function by weight thereof. Furthermore, if the mass 19 is enlarged as large as possible, a periphery of the bracket 13 is susceptible to be large-sized. That would be disadvantageous since the space is very crowded with a plurality of parts.